Are you talking about adding this to a new pond or an uncycled pond?
If you are wanting something to help clean your pond from debris:
Clean your filters thoroughly
Take a Pond Vac, Shop Vac, etc and clean the bottom,(I assume you don't have a BD) enough to do a 10-20% Water Change would be wonderful.
You will be amazed if you do Weekly Water Changes. Definately not $20 a pop and much more healthy of an environment for your fish.